Various gravity separators are known in the prior art that utilize a flow of air and vibration for separating and grading particulate matter, such as grain or minerals, as to weight or size. See for example, U.S. Pat. Nos. 3,486,620 issued Dec. 30, 1969 to Stolle, and 1,194,477 issued Aug. 15, 1916 to Chevalier et al. Such gravity separators employ a gently sloping and vibrating deck that is perforate to allow the air to flow therethrough. Particulate matter placed on a lower corner of the deck will be partially supported off the deck by the air flow so that it can move in a fluid fashion. The vibration urges the particles up the gentle slope of the deck wherein the heaviest particles reach the highest point of the deck. Thus, the material is classified uniformally by decreasing weight in a direction from the top end to the bottom end of the deck.
The vibratory motion is imparted to the deck by a drive rod or rods pivotally connected on one end to the deck and on their other end to an eccentric shaft. Rotation of the shaft moves the rod in a back and forth motion, thereby vibrating the deck. A counterweight mechanism is generally employed to oppose the motion of the deck to minimize vibration in the machine caused by the deck movement. However, a counterweight mechanism does not eliminate all vibration associated with operation of current art gravity separators. Substantial vibration continues to occur as a result of the motion of various components, other than the deck. Such vibration, overtime, can cause damage to these various parts, and thus, premature failure of the machine.
In addition, it has become increasingly important, particularly with separators used to process grains, that the amount of energy required to operate the machine, and thus the cost of operating the machine, be minimized. Prior art gravity separators work satisfactorily but consume a substantial amount of energy. A major inefficiency concerns the placement of the fan, for creating the air flow through the deck, in a position substantially away from the deck. See for example, U.S. Pat. No. 2,257,614 issued Sept. 30, 1941 to Sutton et al. As a result of such placement, air cannot be delivered directly and evenly through the deck, thereby decreasing the effectiveness of the airflow produced by the fan.